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  • Küçük Resim
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    Clinical utility of a 1.5 T magnetic resonance imaging-guided linear accelerator during conventionally fractionated and hypofractionated prostate cancer radiotherapy
    (PMC, 2022) Türkkan, Görkem; Bilici, Nazlı; Sertel, Hüseyin; Keşküş, Yavuz; Alkaya, Sercan; Özkırım, Müge; Fayda, Merdan
    Purpose: To report our initial experience with 1.5 T magnetic resonance imaging (MRI) linear accelerator (LINAC) in prostate cancer radiotherapy in terms of its use in a radiation oncology clinic. Methods: The medical records of 14 prostate cancer patients treated with MRI-guided radiotherapy were retrospectively evaluated. The fraction time, adapt-to-position (ATP):adapt-to-shape (ATS) usage rate, machine-associated treatment interruption rate, median gamma pass rate, the percentage of planning target volume receiving at least 95% of the prescription dose coverage value of each ATS fraction, the effect of the learning curve on the fraction time and radiation-related acute gastrointestinal and genitourinary toxicities were evaluated. Results: Fourteen patients have completed their treatment receiving a total of 375 fractions. Six patients (42%) were treated with the moderately hypofractionated regimen, five patients (36%) with conventionally fractionated, and three patients (22%) with the ultra-hypofractionated radiotherapy regimens. The ATP : ATS usage ratio was 3:372. The median fraction time was 46 min (range, 24-81 min). For the 3%/3 mm criterion, median gamma pass rate was 99.4% (range, 94.6-100%). Machine-related treatment interruptions were observed in 11 (2.9%) of 375 fractions, but this interruption rate decreased from 4.1% to 0.8%, after an upgrade. Three patients (22%) had gastrointestinal and five patients (36%) had genitourinary toxicity. No ?grade 3 toxicity was observed. Conclusion: 1.5 T MRI-LINAC device could be used as a conventional LINAC device, when the conditions of the radiotherapy center are appropriate. MRI-guided prostate radiotherapy is safe and feasible, and high-quality studies with a larger number of patients and long-term results are needed to better evaluate this new technology.
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    Dosimetric comparison of volumetric-modulated arc therapy and dynamic conformal arc therapy in three-fraction single-isocenter stereotactic radiosurgery for multiple brain metastases
    (KARE PUBL, 2022) Türkkan, Görkem; Bilici, Nazlı; Sertel, Hüseyin; Tavlı, Büşra; Özkırım, Müge; Fayda, Merdan
    Abstract OBJECTIVE The objective of the study was to compare single-isocenter volumetric-modulated arc therapy (VMAT) and dynamic conformal arc therapy (DCAT) techniques in patients who received multifraction stereotactic radiosurgery (SRS) for multiple brain metastases. METHODS Twenty-one patients who were treated with a radiation dose of 27 Gy in three fractions were replanned. Roth VMAT and DCAT plans with single isocenter were obtained for each patient. Plan quality indices, cumulative monitor unit (MU) values, maximum dose for organs at risk, and mean dose, V19.6(Gy), and V23.1(Gy) for healthy brain tissue were compared. RESULTS The conformity index (11=0.0002), gradient index (p=0.003), maximum dose for brainstem (p=0.016) and mean dose (p=0.00007), V19.6(Gy) (p=0.00006), and V23.1(Gy) (p=0.00006) values for healthy brain tissue were significantly superior in the VMAT technique, compared to DCAT technique. In addition, a trend toward significance for achieving lower maximum dose value to the optic nerves and/or pathway was observed with VMAT (11=0.073). DCAT provided significantly lower MU values (3097.14 vs. 1479.09; p=0.00006). CONCLUSION VMAT was able to provide better target conformity and lower risk of brain radionecrosis at least dosimetrically in multifraction SRS for patients with multiple brain metastases. DCAT may he chosen in patients with relatively poor performance status or low tolerance to long-lasting radiotherapy sessions.
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    Preoperative radiotherapy for rectal cancer: A bibliometric analysis of the 100 most-cited research articles
    (NJCPONLİNE, 2022) Türkkan, Görkem; Alkan, A.
    Background and Aims: Preoperative long-course radio-chemotherapy (LC-RCHT) or preoperative short-course radiotherapy (SC-RT) are widely used in the treatment of locally advanced rectal cancer (LARC). This study aimed to evaluate the 100 most-cited research articles focused on preoperative radiotherapy for rectal cancer to reveal existing academic trends and the direction of therapeutic research. Materials and Methods: This was a retrospective study based on publicly accessible data. The Web of Science database was used to identify the 100 most-cited articles. Results: The median values for total citation and average citation per year (CPY) were 240.50 (range, 150–3787) and 17.32 (5.03–222.76), respectively. Randomized (median: 24.88 vs 13.32, P = 0.001) and funded (median: 27.33 vs 14.73, P = 0.002) studies had more CPY than those with opposite characteristics. No significant difference was found between studies using SC?RT and LC?RCHT, in terms of average CPY (median: 15.27 for SC?RT vs 18.36 for LC-RCHT, P = 0.303). In terms of the primary aim of the investigation, studies investigating non-operative treatment strategies had higher CPY than those investigating other subcategories (p = 0.029). Conclusion: Randomized studies, funded studies, and studies investigating non-operative treatment were associated with more CPY. There remains equal interest in preoperative SC-RT and LC-RCHT for rectal cancer.
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    Prognostic importance of microvessel density, VEGF expression and perineural invasion in laryngeal cancer treated with adjuvant radiotherapy
    (Indian Association of Pathologists & Microbiologists, 2022) Harmankaya, Ilknur; Caloglu, Vuslat Yurut; Tastekin, Ebru; Türkkan, Görkem; Caloglu, Murat; Uzal,Cem
    Background and aims: We aimed to investigate the prognostic importance of the microvessel density (MVD) value, the vascular endothelial growth factor (VEGF) expression, and the presence of perineural invasion (PNI) in laryngeal cancer (LSCC) patients. Methods: Pathological specimens of 62 LSCC patients were assessed for the evaluation of the MVD value, the VEGF expression level, and the presence of PNI of the tumors. The tumor characteristics and prognostic effects of these parameters on local control (LC) and overall survival (OS) were analyzed. Statistical analysis: Descriptive analyses were done using frequencies for the demographic variables. The survival estimates were calculated by the Kaplan-Meier survival curves. The effects of the parameters on LC and OS were investigated by using the log-rank test comparing the survival rates. Cox regression analysis was used for multivariable analysis. Results: The 5-year LC and OS rates of the 62 LSCC patients were 64.5 and 53.9%, respectively. Twenty-two patients (35.5%) had PNI and the frequency of PNI was higher in the patients with a high-grade disease (P = 0.01). The MVD value was higher in the tumors of older patients (P = 0.035) and was correlated with the VEGF expression (P = 0.009). A higher tumor grade was related to a higher VEGF expression (P = 0.01) and the increase in the VEGF expression was associated with a significant decrease in the OS (P = 0.03). Conclusion: The VEGF expression, the MVD value, and the presence of PNI had no prognostic significance on the LC in the LSCC patients while only the VEGF expression was associated with the OS.
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    Radiotherapy-induced cardiotoxicity after the treatment of pulmonary and mediastinal solid tumors
    (Istanbul Tip Fakultesi, 2022) Saynak, Mert; Türkkan, Görkem; Nurlu, Dilek; Ozguven, Yildiray
    Thoracic tumors are extremely common and radiotherapy plays an important role in the treatment of these malignancies. Cardiac radiation exposure which is inevitable during thoracic radiotherapy may damage the heart muscle, valves, or coronary arteries. If a malignant thoracic disease can be successfully treated with the contribution of radiotherapy, long-term cardiac toxicity will become a critical factor in determining survival. Therefore, radiation oncologists have recently focused on efforts to provide local disease control without causing toxicity. Over time, advances in radiotherapy techniques have made it possible to significantly limit the dose of cardiac structures while effectively treating the thoracic tumor. Intensity-modulated radiotherapy techniques are beneficial in reducing the cardiac dose and therefore cardiac toxicity. Advanced particle radiotherapy applications such as proton therapy have the potential to improve tumor cell killing efficiency and reduce the risk of cardiac complications. Close and long-term cooperation between radiation oncologists and cardiologists is important in the follow-up of patients undergoing thoracic radiotherapy. © 2022, Turkish Society for Radiation Oncology.